Examination of the vegetative part of the nervous system or the sensory functions is carried out by supplying sensory stimuli to the organism under examination and by measuring the response to such a stimulus. The evoked response to a stimulus can be obtained from several variables of an organism, for example, skin potential, skin impedance, skin temperature, electrical signals from deep tissue e.g. muscle potentials, changes in the fluid production, e.g. the water production i.e. the water secretion or water content of tissue cells etc.
International patent application WO-A-9,014,749 discloses a method and an apparatus of the type mentioned above for analyzing neural sickness from the vegetative part of the nervous system of an organism, in response to sensory stimuli supplied to the organism under examination. Said stimuli can be chosen from a group of sensory stimuli, such as visual stimuli, sound stimuli, olfactory stimuli, gustatory stimuli, tactile stimuli or pain stimuli. The neural signals are achieved from measuring the evoked response of the organism to such a stimulus.
The results of said measurements can be evaluated and classified into different types, i.e. hypersympatheticotonia, pre-sympatheticotonia, vegetative normotonia (eutonia), preparasympatheticotonia and hyperparasympatheticotonia. By correlation of said types and other medical data, diagnosis on existing diseases or the probability of falling ill with a specific disease in future can be estimated.
International patent application PCT/NL91/00071, not a prior publication, discloses a method for measuring sensory functions of an organism, such as hearing, sight, smell, touch and pain, providing an objective assessment of the functioning of the sense organs, i.e. without the need for report by the organism under examination. In this method, specific stimuli are supplied to the organism, adapted to the sense under investigation i.e. auditory, visual, olfactory, gustatory, tactile, or pain stimuli. The reaction to such a specific stimulus is determined by measuring the evoked response of the organism.
It has been found that the evoked response by a sequence of stimuli of a certain type, e.g. light or sound, applied in a rhythmical manner is not stable over time. It is to say, as the time of stimulation increases, the response of the nervous system to said sequence of stimuli undesirable alters and/or decreases. Further, repeated investigation of the organs of sense, for example on the next day, can also have an adverse effect on the response of the organism to a specific stimulus or sequence of stimuli.